Drag and drop: glisser Restriced zone

button.onPress = function() {
  startDrag(this);
  if(this.hitTest(polygon)===false){
   stopDrag;
  }
}
button.onRelease = function() {
  stopDrag;
}

if(this.hitTest(polygon) === false)
  stopDrag;

MovieClip.prototype.confineDrag = function(guide){
    this.onPress = function(){
        this.onMouseMove = function(){/*using mouse instead of enterFrame saves CPU on mouse idle*/
            if(guide.hitTest(_xmouse,_ymouse,true)){/*this use of hitTest compares _xmouse & _ymouse to cordinates of paramater "guide" which is a movieClip passed to the prototype, true tells flash to evaluate the actual shape of the guide instead of just the bounding rectangle.*/
                this._x = _xmouse;/*place this at xmMouse if hitTest returns true*/
                this._y = _ymouse;
            }
        }
    }
    this.onRelease = function(){
        delete this.onMouseMove;/*delete mouseMove event, this may need to be called onReleaseOutside as well, "this.onRelease=this.onReleaseOutside= function()" */
    }
}
square.confineDrag(_root.oval);/*apply prototype to square with oval as hitTest guide*/

MovieClip.prototype.confineDrag = function(guide) {
  this.onPress = function(){
   this.onMouseMove = function(){
     if(guide.hitTest(_xmouse,_ymouse,true)){
      this._x = _xmouse;
      this._y = _ymouse;
     }
   }
  }
  this.onRelease = this.onReleaseOutside = function(){
   delete this.onMouseMove;
  }
}

btn.confineDrag(_root.polygon);